It is universally known that the heating efficiency of the conventional fireplace (wood, charcoal or coal burning, typically) is extremely low. A great deal of the combustion heat is largely lost up the chimney in the form of combustion gases, smoke and vapors, as well as heated convection currents. Next, the necessary combustion draft into the fireplace and up the chimney must draw cold air from outside the dwelling into the house and the room housing the fireplace through various openings in the structural members of the dwelling, including door frames, window casings and the like. The radiation from the five alone often serves as the primary source of room heat.
A considerable number of devices and constructions have been developed in the past, utilized and are presently available on the market in various forms to attempt to improve the effectiveness and efficiency of fireplace heating and the achievement of more efficient use of the combustion energy of fuel. With the prices of natural gas, fuel oil, coal and wood all skyrocketing and multiplying, the problem of efficient fuel and energy utilization has become a most serious business indeed. In dwellings which have fireplaces and where such fireplaces are used as auxiliary, supplemental or even primary sources of heat for the dwelling or portions thereof, it is clearly necessary to increase the efficiency of fireplaces by extracting more of the waste heat and circulating it into the room in which the fireplace is located and the balance of the house.
It is not unusual to find dwellings with a conventional central heating system of the forced air type, one or more wood or coal burning stoves and one or more fireplaces. Each of these heat sources has been the subject of intense analytical and cirtical study to attempt to improve the efficiency, as well as safety, of their use. This particular invention is directed specifically to fireplaces wherein there is provided a recessed chamber, typically within the wall of a room of a dwelling, the chamber being constructed of and lined with fire resistent materials, there being a flue at the upper and rear portion of the fireplace chamber, with damper control of air moving from the fireplace chamber into the flue, the flue communicating with a chimney or exhaust channel.
It is understood, as noted, that various fuels are employed in fireplaces, particularly wood, per se, powdered and compressed wood, charcoal, coal and the like. A grate construction is typically provided within the fireplace to contain the fuel to be burned, the grate spacing the fuel members, pieces and chunks upwardly from the floor of the fireplace chamber to enable air circulation through the combustion fuel and, as well, permit accumulation of residue and ash therebelow in such a manner as to not impede the burnout of the original charge of materials, as well as cleanout of the fireplace before the next charge of combustible materials. Improvements have been made in grate constructions to arrange fuels of various sorts for the most efficient combustion and effective production of heat, particularly radiant heat, into the room.
It has come to be recognized as general principles, in dealing with fireplace fuel combustion, that certain control measures, as well as structural provisions, increase efficiency of energy use. In the first place, it is advantageous to close the front of the fireplace with a transparent cover in order to control the access of air from the room containing the fireplace into the fireplace compartment or chamber. Secondly, the inflow of air from the room or space containing the fireplace must be controlled to regulate the quantity of combustion which takes place in the fireplace. Thirdly, mechanical structures involving hollow tubes, passageways and compartments may be placed within the fireplace chamber or compartment in various arrays and positions in order to absorb some of the heat of the fire. Air from the room or liquids may be circulated through these pipes, tubes, constructions and the like to transfer the absorbed heat into the space which is desired to be heated by the fireplace.
Nevertheless, despite the development of these adjuncts and accessories to fireplace structure and use, the most efficient manner and means for maximizing the control of energy produced by a fire in a fireplace has not yet been provided. This goal, so intensely important and significant to the present society, as well as the future, in the subject of this invention.
Three of the most commonly used forms of heating living and dwelling spaces are forced air furnace systems, wood and coal burning free standing stoves and fireplaces. With respect to the combustion carried out in each of these systems, there is provided a flue carrying off the combustion gases. Such combustion gases must be removed from the living and dwelling space because they are dangerous to life. Means have previously been sought to safely extract lost quantities of heat from these combustion gases in order to make the actual heating of the living space in question more efficient.
For example, it is known to jacket the flue conduits carrying the hot exhaust gases and combustion products and flow heat exchanging fluid therethrough. It is additionally known to interpose some heat absorbing object or structure in the flow path of the hot exahust gases in such conduits to extract some fraction of the waste energy therefrom. Heat gathered in the fluid passing through the conduit jacket or heat exchanging structure or barrier in the conduit is passed back into the room, dwelling space or basement where the heating device is located, typically carried by the fluid.
The heat exchanging medium which has picked up some of the excess heat from the combustion gases may be ambient air circulated from the room containing the heating device and recycled back thereto. If the heat exchanging fluid or medium is liquid, it may transfer heat back to the desired zone through fin type heat exchangers over which interior zone air is moved or blown. In forced air furnace systems heat may be transferred into the furnace air return ducts.
The subject invention is devoted to the extraction of maximum heat from a conventional fireplace while coupling such action and effect with the actual control and manipulation of the combustion in the fireplace so as to maximize efficiency of combustion and minimal use of fuel as well as extraction of heat in a useful manner therefrom.